Testing the impact of reworking on the isochronicity of tephras deposited in diverse sedimentary environments

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This project will improve the ways we interpret and utilize the record of sediments that document the Earth’s geologic history. New methods will be developed to define the age of tephras, sediment that originates from volcanic eruptions, and well-established methods will be used to better understand paleolake level fluctuation in the Great Basin of the U.S. in Nevada. This will aid in reconstruction of paleoclimate and landscape dynamics which contributes to understanding modern changes to climate and informs hazard mitigation, particularly as it relates to drought and desertification in the Great Basin and western U.S. Owing to its contribution to understanding drought hazards, the project contributes to the national health, prosperity, and welfare of the U.S. by increasing knowledge needed for resiliency to global and environmental change. The project also will provide training and support to early and mid-career women and outreach on topics investigated to an audience of interested stakeholders, particularly in the Great Basin in Nevada. Tephras are sediments that comprise volcanically erupted material. An outstanding problem in using tephras to accurately interpret paleoclimate and landscape phenomenon is identifying when they were deposited. This project will resolve questions related to defining the timing of tephra deposition using luminescence dating, which is a burial age dating approach that finds the time of the last exposure of sediment to light or heat. In this project, questions about the window of geological time in which tephras are deposited will be tested. The timescales of tephra reworking after deposition will also be tested. These questions are critical to using tephras as markers of time in the sedimentary record. This study is being conducted in the Great Basin of the U.S. because existing data allows us to test our methods and resolve conflicting interpretations of paleo lake-levels that rely on the tephra record. This work will yield a reliable dating methods to date tephras that are older than the 35 ka upper limit for reliable radiocarbon and younger than the 120 ka lower limit of reliable K/Ar and 40Ar/39Ar dating techniques. This work will also contribute to improving interpretations about paleoclimate and reconstructions of landscape dynamics, such as lake-level fluctuations, that are made from tephra correlations.This award reflects NSF's statutory mission and has been deemed worthy of support through evaluation using the Foundation's intellectual merit and broader impacts review criteria.